US officials on Monday found the body of "Glee" actress Naya Rivera in the Californian lake where she drowned last week during a boat trip with her four-year-old son.

Rivera's body was retrieved and an initial examination found no evidence of foul play or suicide, Ventura County Sheriff Bill Ayub told a press conference.

"We are confident the body we found is that of Naya Rivera," said Ayub, pointing to the location, appearance, clothing and condition of the body.

Her body was being taken to a medical examiner's office for a full autopsy and confirmation of her identity from dental records, though no other missing persons have been reported at Lake Piru, he added.

Rivera, 33, is believed to have accidentally drowned after renting the boat with her young son at the camping and recreational hotspot around an hour's drive northwest of Los Angeles.

She vanished on Wednesday afternoon, and a massive search involving divers, patrol boats and helicopters was launched after her sleeping son was spotted drifting alone in a boat on the lake.

The son later told investigators that Rivera had helped him into the boat before "he looked back and saw her disappear under the surface of the water," said the sheriff.

Ayub pointed to the lake's strong currents as a possible cause of a fatal accident.

"The idea perhaps being that the boat started drifting -- it was unanchored -- and that she mustered enough energy to get her son back onto the boat, but not enough to save herself," he said.

The lake has been closed to the public since Wednesday, with around 100 personnel, including the US Coast Guard and rescuers from neighboring counties, joining the search.

Search teams used footage from video messaging calls Rivera made from the boat before her disappearance, as well as interviews with her son, to scour portions of the lake bed for her remains over six days, with no success.

"We believe she was concealed within some of the shrubbery on the floor bed of the lake" before eventually floating to the surface due to natural decomposition, said Ayyub.

With less than one foot (30 centimeters) of visibility underwater in daylight, the recovery operation was a "complex search effort" even with use of sonar equipment, he said.

Rivera was best known for her role as high school cheerleader Santana Lopez in "Glee."

She starred for six seasons in the wildly popular musical television series set in a US high school that ended in 2015.

The "Glee" cast has been struck by tragedy before.

Actor Mark Salling took his own life in 2018, weeks before being sentenced for possession of child pornography.

Canadian castmate Cory Monteith died in July 2013 of an overdose of drugs and alcohol.